The present invention relates to a method of manufacturing a rigid foamed product, and more particularly to a method of manufacturing a rigid foamed product suitable for filling up a hollow portion of a formed steel article and the like for reinforcement.
In general, conventional rigid foamed products are produced by adding fibrous materials to resins to form resin complexes and subsequently foaming the resin complexes, or by adding porous fillers to resins to form porous resin products.
The conventional methods utilizing the fibrous materials described above may produce rigid formed products which satisfy rigidity requirements. However, most of such methods cannot produce sufficiently lightweight formed products since each product has merely a limited resin expansion ratio of up to about 2 because of release of gases generated through the fibrous materials. If the resins used are replaced with highly foamable resinous materials which may exhibit a high expansion ratio greater than 2, these methods cannot also produce fiber reinforced foamed products having a high expansion ratio of greater than 2 since the gases generated are released through the fibrous materials. Further, in the methods utilizing the porous fillers, it is difficult to mount the products in hollow portions (hereinafter also referred to as cavities) formed within a formed metal article.